Study On Heat Transfer And Friction Behaviors In Mould Of Slab Continuous Casting

The mould is the core component of continuous caster for primary cooling and initial shell forming of liquid steel.There is a complex interaction of thermo-mechanical behaviors between mould and strand.The states of heat transfer,solidification,friction and lubrication determine the mould working conditions,furthermore,determine strand surface quality and production capacity of continuous caster.At present,the key of mould monitoring technique is on-line detection of thermo-mechanical behaviors,the aim of which is to understand the status of heat transfer,friction and lubrication between mould and strand immediately,in order to provide the support for on-line forecast and control of strand quality.Therefore,it complies with the basic requirement of the development of high efficiency continuous casting technology,to analyze and master the mechanism of thermo-mechanical interaction behaviors in mould,and to develop and apply the calculation methods of heat transfer and friction in mould based on measured data.In this paper,the mould of continuous slab caster is taken as the research object,the study is spread around heat transfer and friction behaviors occurring in the mould.With a view to drive and promote the production application of the study on mould thermo-mechanical behaviors,the achievements and shortage of previous works are summarized,the simulating and detecting studies on heat transfer,solidification,friction and lubrication behaviors are conducted.Firstly,based on the measured data of mould temperature during slab continuous casting,an inverse problem model is built,and the mould heat transfer and the strand solidification in the practical production are analyzed.Secondly, the mathematical model of friction behavior on mould/slag/strand interface is derived and built,and the lubrication behavior in mould is discussed.Thirdly,based on the slab caster equipped with hydraulic oscillators the transient detecting model of mould friction is researched and built,and the detection results of mould friction are analyzed.Finally, integrating the contents of simulating calculation and detection experiment,the application idea of combined monitoring of heat transfer and friction states in mould is put forward with primary design and discussion.An inverse problem model of mould heat transfer in slab continuous casting is researched and built aiming at the installation characteristics of thermocouples in slab mould. Based on measured temperature data the behaviors of mould heat transfer and strand solidification are simulated,and then the distributions of heat flux and shell thickness,and the effect of casting speed in the practical production are detailedly analyzed.And the rationality and feasibility of heat transfer calculation is validated.The mathematical model to describe friction behavior on mould/slag/strand interface is built with introducing mixed lubrication theory by well defined and divided different contacting and lubricating states on strand surface.Using the calculation results of mould heat transfer based on measuring data mentioned above,the thickness distribution of liquid slag film between mould and strand,slag lubrication status,frictional stress variation on the interface and their influence factors are analyzed.After that a detecting method of thermal lubrication and friction state of mould fluxes is put forward,which can be used for production field.On the basis of the slab caster equipped with hydraulic oscillators and the classical forced oscillation theory,the mould force situation during oscillation is analyzed and the detection idea of mould friction is determined.The calculation model of cylinder force at empty state is regressed,and the rationality and the range of parameters are discussed.Based on the detecting results of mould friction,frictional transient behavior,relative parameters variation,effect of oscillation mode and abnormal status are analyzed.The results show that the transient friction approximately changes with oscillation velocity during the normal state, both of which coincide well;abnormal fluctuation of friction would occur before the breakout with bad coincidence between friction and velocity.